JP2010103500A - Organic electroluminescent element, method for manufacturing the same, image display unit and illuminating device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element which forms a light-emitting medium layer, the organic electroluminescent element having a hole transport layer having a high light extraction efficiency. <P>SOLUTION: In the organic electroluminescent element comprising at least a plurality of layers including the hole transport layer 104 made of an inorganic compound and an organic light-emitting layer 106 between a first electrode 102 and a second electrode 107 on a substrate, the high light extraction efficiency can be obtained by reflecting light emitted from the organic light-emitting layer by the hole transport layer. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic electroluminescent element used in a self-luminous display device and a lighting device.

  An organic electroluminescent element (hereinafter abbreviated as an organic EL element) is formed by forming a hole transporting layer made of a hole transporting material or a light emitting layer made of an organic light emitting material between two opposing electrodes, and passing an electric current. Display light emitted from the organic light emitting layer is taken out from the light transmissive electrode, and has attracted attention as a light emitting element capable of high luminance light emission by low voltage direct current driving despite its simple structure. However, in the organic EL element, the emitted light having a critical angle or more determined by the difference in refractive index at the electrode, the organic light emitting layer, and the interface between the substrate and each layer is totally reflected and confined inside, and lost as guided light. Further, since there is a reduction in the area of the light emitting pixel due to the TFT, there is a problem that the light extraction efficiency from the organic light emitting layer to the outside is poor and the device characteristics are deteriorated.

  In order to improve the reduction in light extraction efficiency, a top emission type (hereinafter referred to as a top emission structure) organic EL element has been proposed for reducing the light emitting pixel area by the TFT (see Patent Document 1). In the display device having a configuration using the means for improving the light extraction efficiency by the top emission structure, it is possible to avoid the reduction of the light emitting pixel area due to the TFT, but there is a loss for the light emitted in the back direction. . In Patent Document 1, the light extraction efficiency is improved by forming a reflective layer on the back electrode or using a reflective material for the electrode.

  However, the emitted light that disappears in the organic thin film cannot be extracted efficiently. In other words, the above method cannot cope with light emitted by scattering in the organic thin film or absorption by the partition walls partitioning the light emitting layer.

JP 2006-100137 A

  Accordingly, an object of the present invention is to provide an organic electroluminescent device capable of improving the light extraction efficiency of emitted light from the organic light emitting layer to the outside and improving the device characteristics.

The present invention has been made in view of the above problems,
The invention according to claim 1 is an organic electroluminescent device having at least a hole transport layer made of an inorganic compound and an organic light emitting layer between a first electrode and a second electrode on a substrate, The organic electroluminescence device is characterized in that light emitted from the light emitting layer is reflected by the hole transport layer.
The invention according to claim 2 is the organic electroluminescent element according to claim 1, wherein the inorganic compound is an inorganic compound containing one or more transition metals.

The invention according to claim 3 is the organic electroluminescent element according to claim 1 or 2, wherein the inorganic compound contains a metal oxide material having oxygen defects and exhibiting a metallic luster.
The invention according to claim 4 is the organic electroluminescent element according to claim 3, wherein a work function of the metal oxide material is 4.0 eV or more and 6.5 eV or less.
The invention according to claim 5 is characterized in that the metal oxide material is any one of titanium oxide, nickel oxide, tungsten oxide, molybdenum oxide, silver oxide, cobalt oxide, chromium oxide, ruthenium oxide, and iridium oxide. It is an organic electroluminescent element of Claim 3 or 4.
According to a sixth aspect of the invention, the inorganic compound includes a hole transport material and a metal oxide material having an oxygen defect and exhibiting a metallic luster, and the hole transport material includes Cu ₂ O and Cr ₂ O. ₃ , Mn ₂ O ₃ , NiO, CoO, Pr ₂ O ₃ , Ag ₂ O, MoO ₂ , ZnO, TiO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O ₅ , MoO ₃ , WO ₃ , MnO It claims 3, characterized in that it comprises any of ₂ to an organic electroluminescence device according to any one of the 5.
The invention according to claim 7 is characterized in that an average reflectance of the hole transport layer with respect to light emitted from the organic light emitting layer is 50% or more. It is an organic electroluminescent element.
The invention according to claim 8 is the organic electroluminescent element according to any one of claims 1 to 7, wherein the hole transport layer has a thickness of 10 nm to 100 nm.
The invention according to claim 9 is the organic electroluminescence device according to any one of claims 1 to 8, further comprising a partition partitioning at least the organic light emitting layer into a plurality of pixels.
The invention according to claim 10 is the organic electroluminescent element according to claim 9, wherein the hole transport layer covers at least a part of the partition wall.
According to an eleventh aspect of the present invention, the second electrode is a transparent electrode, and the first electrode and the second electrode are laminated in the order of the first electrode, the hole transport layer, and the organic light emitting layer. The organic electroluminescent element according to claim 1, wherein the organic electroluminescent element is formed.
In the invention according to claim 12, the first electrode is a transparent electrode, and the first electrode, the organic light emitting layer, and the hole transport layer are stacked in this order between the first electrode and the second electrode. The organic electroluminescent element according to claim 1, wherein the organic electroluminescent element is formed.
A thirteenth aspect of the present invention is an image display device using the organic electroluminescent element according to any one of the first to twelfth aspects as a display element.
The invention according to claim 14 is an illuminating device characterized in that the organic electroluminescent element according to any one of claims 1 to 13 is used as a light emitting element.
The invention according to claim 15 is a method of manufacturing an organic electroluminescent device having at least a hole transport layer made of an inorganic compound and an organic light emitting layer between a first electrode and a second electrode on a substrate. Forming a first electrode on the substrate, forming a hole transport layer reflecting light emitted from the organic light emitting layer on the first electrode, and organic light emitting on the hole transport layer. It is a manufacturing method of the organic electroluminescent element which has the process of forming a layer, and the process of forming a 2nd electrode on the said organic light emitting layer.
The invention according to claim 16 is the method of manufacturing an organic electroluminescent element according to claim 15, wherein the hole transport layer is formed by mixing a plurality of inorganic compounds by a dry film forming method.
The invention according to claim 17 is the method of manufacturing an organic electroluminescent element according to claim 16, wherein the hole transport layer is formed by mixing a plurality of inorganic compounds by co-evaporation.
According to an eighteenth aspect of the present invention, the inorganic compound includes a metal oxide, and at least one kind of metal oxide is caused to cause oxygen defects at the time of vapor deposition or after film formation. It is a manufacturing method of an electroluminescent element.
The invention according to claim 19 is characterized in that the organic light emitting layer is formed by depositing an ink containing an organic light emitting material by a wet film forming method. It is a manufacturing method of an electroluminescent element.
According to a twentieth aspect of the present invention, the method includes a step of forming a partition partitioning a plurality of pixels on the substrate, and the hole transport layer is formed over the entire display region including the partition and the first electrode. A method for producing an organic electroluminescent element according to any one of claims 15 to 19.

  In the display element having such a configuration, since the hole transport layer reflects the light emitted from the light emitting layer, it is possible to extract the light that has disappeared as the guided light in the organic thin film. . Furthermore, by covering at least a part of the barrier ribs with the hole transport layer, it is possible to extract the emitted light absorbed by the barrier ribs.

  In addition, as a material for the hole transport layer, an oxide, sulfide, or nitride of an inorganic compound containing at least one transition metal is used as a hole transport material for an organic EL device by forming a single layer, a stacked layer, or a mixed layer. It became possible to form a thin film of 100 nm or less with high reflectivity as well as conductivity and energy level.

  The organic light emitting display device having the above structure is a hole transport layer that emits light emitted from the light emitting layer, confined in the organic thin film, deactivated as guided light, and display light absorbed by the partition walls. It becomes possible to take out emitted light efficiently by reflecting the light.

It is a schematic sectional drawing of the organic electroluminescent apparatus which concerns on embodiment of this invention. It is a schematic sectional drawing of the laminated part of the organic electroluminescent element of this invention which concerns on embodiment of this invention. It is a schematic sectional drawing of the organic electroluminescent apparatus which concerns on embodiment of this invention. It is a schematic sectional drawing of the organic electroluminescent apparatus which concerns on embodiment of this invention. It is a schematic sectional drawing of the organic electroluminescent apparatus which concerns on embodiment of this invention. 1 is a schematic cross-sectional view of a relief printing apparatus according to an embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings referred to in the following description of the embodiments are for explaining the configuration of the present invention, and the size, thickness, ratio of dimensions, etc. of the respective parts shown in the drawings represent the embodiments as they are. is not.

  FIG. 1 is a cross-sectional view of a display device for explaining an embodiment of the present invention. In the display device 100 using the organic light emitting display element according to the embodiment of the present invention shown in FIG. 1, a first electrode (anode) 102 a provided for each pixel and a first electrode between the pixels are provided on a substrate 101. A partition wall 103 to be partitioned; a hole transport layer 104 formed above the first electrode; an interlayer 105 formed on the hole transport layer; an organic light emitting layer 106 formed on the interlayer; A second electrode (cathode) 107a formed to cover the entire surface of the organic light emitting layer, a first electrode, a partition, a hole transport layer, an interlayer, a light emitting medium layer including an organic light emitting layer, and a second electrode A sealing body 108 in contact with the substrate 101 is provided so as to cover.

  Here, the light emitting medium layer 112 is a layer sandwiched between the first electrode (anode) 102a and the second electrode (cathode) 107a. In the element of FIG. 1, the hole transport layer 104, the interlayer 105, and the organic light emitting layer 106 correspond to the light emitting medium layer. In addition to this, layers such as a hole injection layer, an electron transport layer, and an electron injection layer may be appropriately added.

  2A and 2B are cross-sectional views of the stacked portion of the organic electroluminescent element of the present invention. FIG. 2A shows an example of a top emission type organic electroluminescence device, in which a first electrode (anode) 102a, a hole transport layer 104, an organic light emitting layer 106, and a second electrode (cathode) 107a are stacked on a substrate 101 in this order. Has been. As long as the layers are stacked in this order, the interlayer 105 and other layers may be stacked between them. The second electrode is a transparent electrode, and the light emitted to the second electrode side is transmitted through the second electrode and emitted to the outside. On the other hand, since the light emitted to the first electrode side is reflected by the hole transport layer, it is similarly transmitted through the second electrode and emitted to the outside. Therefore, the extraction efficiency of emitted light to the outside can be improved by the amount reflected by the hole transport layer.

  FIG. 2B shows an example of an inverted structure type organic electroluminescence device, in which a first electrode (cathode) 102b, an organic light emitting layer 106, a hole transport layer 104, and a second electrode (anode) 107b are stacked on a substrate 101 in this order. Has been. As long as the layers are stacked in this order, the interlayer 105 and other layers may be stacked between them. The substrate 101 and the first electrode are transparent electrodes, and the light emitted to the first electrode side passes through the first electrode and the substrate and is emitted to the outside. On the other hand, since the light emitted to the second electrode side is reflected by the hole transport layer, it is similarly transmitted through the first electrode and emitted to the outside. Therefore, as in the case of the top emission type, the efficiency of extracting emitted light to the outside can be improved by the amount reflected by the hole transport layer. The following description is based on a top emission type organic electroluminescent device, but the reverse structure type is also applied by switching the cathode and the anode and reversing the order of the light emitting medium layers.

  The hole transport layer 104 according to the organic electroluminescent element of the present invention has a property of reflecting the light emitted from the organic light emitting layer, as is apparent from the above principle. Specifically, the reflectivity of the hole transport layer is preferably 50% or more, more preferably 70% or more, as a total average with respect to the wavelength of light emitted from the light emitting layer. That is, an organic light emitting element used in a full color organic light emitting display device needs to have a reflectance of 50% or more with respect to each emission light in the visible light region, and thus has a reflection of 50% or more in the visible light region. A hole transport layer material having a rate is preferred. The same applies to organic light-emitting elements used in white light illumination devices.

  On the other hand, in an organic electroluminescent element emitting monochromatic light, it is sufficient that the light is reflected at the wavelength of the emitted light. In addition, although the number of processes increases, even in a full-color organic light emitting display device, by patterning the hole transport layer and forming the hole transport layer by changing the film forming material for each pixel of each emission color, It is also possible to use a material having a high reflectance only at a specific wavelength.

The physical property value of the hole transport layer preferably has a work function equal to or higher than that of the anode (102a, 102b). This is because holes are efficiently injected from the anode into the interlayer or light emitting layer. Although it varies depending on the material of the anode and the material of the upper layer, 4.5 eV or more and 6.5 eV or less can be used, and when the anode is ITO or IZO, 5.0 eV or more and 6.0 eV or less can be preferably used. is there. Although the resistivity of the hole transport layer varies depending on the patterning method, it is preferably 1 × 10 ^{3 to} 5 × 10 ⁸ Ω · m, more preferably 5 × 10 ⁴ to 1 in view of preventing leakage to adjacent pixels. × 10 ⁷ Ω · m. Moreover, although the thickness of a positive hole transport layer changes with material characteristics, when the above-mentioned resistivity is considered, it is preferable that it is 100 nm or less. On the other hand, if the thickness of the hole transport layer is small, light is transmitted and the extraction efficiency decreases, so that the thickness is preferably 10 nm or more.

  As shown in FIG. 3, in the case of a top emission type organic light emitting display device, when the hole transport layer 104 is formed on the substrate having the partition wall formed on the substrate, the hole transport is also performed on the partition wall. It is preferable to form a layer. This is because the hole transport layer covers the partition wall, so that the emitted light that has been guided by the light-emitting medium layer or scattered and absorbed by the partition wall can also be reflected, and the extraction efficiency to the outside can be improved. is there. In addition, since a hole transport layer may be formed on the entire surface of the display region including the light emitting region on the first electrode 102 and the partition wall, patterning and alignment for each pixel are unnecessary, and formation is easy. . Alternatively, as shown in FIG. 4, patterning may be performed so that only the upper part of the partition wall 103 is not formed. By covering the vicinity of the light emitting medium layer formed on the hole transport layer without covering the entire partition wall, light guided or scattered from the light emitting medium layer can be reflected.

  The material of the substrate 101 is, for example, glass or quartz, polypropylene, polyethersulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, or the like, or top In the case of an emission type organic light emitting field device, in addition to the above plastic film and sheet, metal oxides such as silicon oxide and aluminum oxide, metal fluorides such as aluminum fluoride and magnesium fluoride, nitriding Translucent base materials in which a single layer or a laminated layer of a polymer resin film such as a metal nitride such as silicon or aluminum nitride, a metal oxynitride such as silicon oxynitride, an acrylic resin, an epoxy resin, a silicone resin, or a polyester resin ,Aluminum Non-translucent base materials in which a metal film such as aluminum, copper, nickel, and stainless steel is laminated on a metal foil, sheet, plate, plastic film or sheet such as um or stainless steel can be used in the present invention. It is not limited.

  The light extraction surface of the organic light emitting display device 100 may be formed from the electrode side facing the substrate 101. The substrate 101 made of these materials has a moisture-proof treatment or hydrophobicity by forming an inorganic film or applying a resin on the entire surface or one surface of the substrate 101 in order to prevent moisture or oxygen from entering the organic light emitting display device 100. It is preferable to have processed. In particular, in order to avoid moisture intrusion into the light emitting medium layer 112, it is preferable to reduce the moisture content and gas permeability coefficient of the substrate 101.

  The first electrode 102 according to the embodiment of the present invention is formed on the substrate 101 and patterned as necessary. When the light emitting layer is formed of a coating type organic light emitting material, which is an organic light emitting element used in a full color light emitting organic light emitting display device, the first electrode 102 is partitioned by a partition wall 103 and becomes a pixel electrode corresponding to each pixel. .

  Examples of the material of the first electrode 102 include metal composite oxides such as ITO (indium tin composite oxide), indium zinc composite oxide, and zinc aluminum composite oxide, metal materials such as gold and platinum, and these metal oxides. Alternatively, a single layer or a laminate of fine particle dispersion films in which fine particles of a metal material are dispersed in an epoxy resin or an acrylic resin can be used, but the present invention is not limited to these.

  When the first electrode 102 is used as an anode, it is preferable to select a material having a high work function such as ITO. When the cathode has an inverse structure, it is preferable to select a material having a low work function such as Ag. In the TFT-driven organic electroluminescence display device, the electrode has only to have a low resistance, and if it has a sheet resistance of 20Ω / □ or less, it can be suitably used.

  As the formation method of the first electrode 102, depending on the material, dry film formation methods such as resistance heating evaporation method, electron beam evaporation method, reactive evaporation method, ion plating method, sputtering method, ink jet printing method, gravure, etc. Existing film forming methods such as a wet film forming method such as a printing method and a screen printing method can be used, but the present invention is not limited to these.

  As a patterning method of the first electrode 102, an existing patterning method such as a mask vapor deposition method, a photolithography method, a wet etching method, or a dry etching method can be used depending on a material and a film forming method.

  The partition wall 103 according to the embodiment of the present invention can be formed so as to partition a light emitting region corresponding to each pixel. Preferably, the first electrode 102 is formed so as to cover the end portion (see FIG. 1). In general, in the active matrix driving type organic light emitting display device 100, the first electrode 102 is formed for each pixel, and each pixel tries to occupy as large an area as possible. It is formed to cover. The most preferable shape of the partition wall 103 is basically a lattice shape that divides the pixel electrodes 102 by the shortest distance.

As a material of the partition wall 103, it is necessary to have insulating properties, and a photosensitive material or the like can be used. The photosensitive material may be a positive type or a negative type, a photo-curing resin of a photo radical polymerization system, a photo cationic polymerization system, or a copolymer containing an acrylonitrile component, polyvinyl phenol, polyvinyl alcohol. , Novolac resin, polyimide resin, cyanoethyl pullulan, and the like can be used. Further, as a partition wall forming _material, it is also possible to use SiO 2, TiO ₂ or the like.

  A preferable height of the partition wall 103 is not less than 0.1 μm and not more than 10 μm, and more preferably not less than 0.5 μm and not more than 2 μm. If it is higher than 10 μm, the formation and sealing of the counter electrode 107 is hindered, and if it is lower than 0.1 μm, the end of the pixel electrode 102 cannot be covered, or the adjacent pixel is short-circuited or mixed when forming the light emitting medium layer 112. It is because it will.

  As a method for forming the partition wall 103, a dry film forming method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method, an ink jet printing method, or a gravure printing method, depending on the material. Existing film forming methods such as a wet film forming method such as a screen printing method can be used, but the present invention is not limited thereto.

  As a patterning method of the partition wall 103, a method in which an inorganic film is uniformly formed on a substrate (the base material 101 and the first electrode 102) according to a material and a film forming method, masked with a resist, and then dry etching is performed. Alternatively, a method of coating a photosensitive resin on a substrate and forming a predetermined pattern by a photolithography method can be mentioned, but the present invention is not limited thereto. Add water-repellent agent to resist and photosensitive resin as necessary, make multilayer structure of hydrophilic material and hydrophobic material, or irradiate with plasma or UV to make water-repellent or hydrophilic to ink after formation It can also be granted.

  In the case of a top emission type organic electroluminescent element, the hole transport layer 104 is formed on the first electrode. Depending on the material, the hole transport layer can be formed by dry film formation methods such as resistance heating vapor deposition, electron beam vapor deposition, reactive vapor deposition, ion plating, sputtering, spin coating, sol-gel, etc. However, the present invention is not limited to these, and a general film forming method can be used. In particular, when a dry film forming method is used, the flatness is high and a uniform hole transport layer can be formed. In addition, as will be described later, since an inorganic film having a mixed composition can be formed by simultaneously forming a hole transport material as a main component and an inorganic material that causes metallic luster, a hole transport layer can be formed. A hole transport layer having a high reflectance can be formed while maintaining the above characteristics.

As a material (hole transport material) of the hole transport layer 104, Cu ₂ O, Cr ₂ O ₃ , Mn ₂ O ₃ , NiO, CoO, Pr ₂ O ₃ , Ag ₂ O, MoO ₂ , ZnO, TiO _{2 are used.} , V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O ₅ , MoO ₃ , WO ₃ , MnO _2, etc. transition metal oxides and single-layer inorganic compounds containing one or more transition metal nitrides and sulfides Alternatively, a stacked structure of a plurality of layers or a mixed layer can be formed.

  The patterning method of the hole transport layer 104 varies depending on the material characteristics and the film formation method, but a solid film formation so as to cover the first electrode 102 and the partition wall 103 is easy. Alternatively, as shown in FIG. 4 described above, patterning may be performed so that only the upper portion of the partition wall 103 is not formed by mask vapor deposition. By covering the vicinity of the light emitting medium layer without covering the entire partition wall, light guided or scattered from the light emitting medium layer can be reflected.

  The hole transport layer can be optimized for work function, resistivity, and reflectance by adjusting the nitridation degree, sulfidation degree, and oxidation degree. Control of the nitridation degree, sulfidation degree, and oxidation degree differs depending on various film forming methods, but when a resistance heating vapor deposition method or a sputtering method is taken as an example, an ion source having a necessary reactive ion is installed in the chamber, or Control is performed during film formation by a method such as purging a gas having a required reactive molecule. Alternatively, heat treatment may be performed in a gas atmosphere required after film formation to control the degree of nitridation, sulfidity, or oxidation of the hole transport layer. Further, when the hole transport layer is a mixture of a plurality of inorganic compounds, the degree of nitridation, degree of sulfidation, and degree of oxidation can be controlled by the mixing ratio.

The hole transport layer having a high reflectivity can be formed, for example, by including a material having a metallic luster in the hole transport layer. Alternatively, in the film forming step, the hole transport layer can be formed by including a material that generates metallic luster by controlling the degree of nitridation, the degree of sulfidization, or the degree of oxidation. Or it can form by including the material which exhibits a metal bond in a positive hole transport layer by mixing with the positive hole transport material (inorganic compound) used as a main component. For example, indium oxide (In ₂ O ₃ ) used in the examples is a material that does not exhibit a metallic luster, but a hole transport layer formed by mixing by co-evaporation with molybdenum oxide as a main component is The reflectance is 50% or more. One reason for exhibiting such reflectance characteristics is considered to exhibit metallic luster due to the release of oxygen from indium oxide in the film formation stage.

More theoretically, in the case of metal oxides, plasma oscillation occurs due to free vacancies in the valence band due to oxygen vacancies, and because the wavelength of the plasma frequency is larger than the emission wavelength of the device, it exhibits a metallic luster. Conceivable. Therefore, the material to be mixed is a metal oxide that generates oxygen vacancies during film formation, and the work function of a single film is 4.0 eV or more in order not to affect the work function of the film when mixed. A material that is 6.5 eV or less is preferred. Examples of inorganic materials added to the hole transport layer in order to generate such a metallic luster include indium oxide, vanadium oxide, titanium oxide (TiO ₂ ), zinc oxide (ZnO), nickel oxide (NiO), and tungsten oxide ( Ta ₂ O ₅ ), molybdenum oxide (MoO ₂ ), silver oxide (Ag ₂ O), cobalt oxide (CoO), chromium oxide (Cr ₂ O ₃ ), ruthenium oxide (RuO ₂ ), iridium oxide (In ₂ O ₃₎ ) And the like. The metal oxide material added to the hole transport layer does not prevent the use of the same material as the hole transport material, and may increase the amount of oxygen deficiency in the hole transport material. However, for example, when forming a hole transport layer in which a hole transport material and a different metal oxide material are mixed by co-evaporation, the difference in the ease of oxygen removal during deposition and the reactivity to the argon ion beam. Because of the difference, oxygen vacancies can be increased only in the metal oxide material to be added, and it is easy to achieve both the characteristics as a hole transport layer and the reflectance.

The film is formed so that oxygen is released from these stable oxides, that is, the oxygen deficiency is 10% or more. Here, the oxygen deficiency is a ratio of oxygen atoms to metal atoms of 0% in the stable state of the added inorganic material. The amount of oxygen deficiency increases as the amount of oxygen atoms decreases. For example, in the case of molybdenum oxide (MoO ₂ ), Mo / O (2) = 0.50 and the deficiency δ is 0% in a stable state. If the ratio of oxygen atoms to one molybdenum oxide atom is 1.5, Mo / O (1.5) = 0.66 and deficiency δ = oxygen deficiency ratio / oxygen when there is no oxygen deficiency Atomic ratio = (2-1.5) / 2 and 25%. The upper limit of the amount of oxygen vacancies is not limited as long as the valence of the metal does not change, that is, the structure of the metal oxide does not change.

  As long as such a film containing oxygen vacancies is a material from which oxygen can be easily released, a film containing oxygen defects can be formed by vapor deposition. Alternatively, oxygen vacancies can be increased by irradiating the formed film with, for example, an argon ion beam.

  Such oxygen vacancies are measured by X-ray photoelectron spectroscopy (XPS) or Auger Electron Spectroscopy (AES), X-ray excited Auger electron spectroscopy (XAES). : X-ray Excited Auger Electron Spectroscopy) can be used for elemental analysis of solid surfaces.

  The amount to be added is not particularly limited as long as it does not impair the function of the hole transport layer, but the added inorganic compound is preferably 70% or less by composition ratio with respect to the whole hole transport layer material. This is because the added inorganic compound basically has a lower resistance and a lower work function than the main component, and if added too much, the characteristics of the hole transport layer may not be maintained. Therefore, it is preferable to mix so that the reflectance is 50% or more within the range satisfying the characteristics of the hole transport layer described above.

  The interlayer 105 according to the embodiment of the present invention can be laminated between the organic light emitting layer and the hole transport layer to improve the light emission lifetime of the device. In the top emission type element structure, the hole transport layer 104 can be stacked after the formation. Usually, the hole transport layer 104 is formed so as to cover it, but patterning may be performed as necessary.

Examples of the material of the interlayer 105 include polyvinyl carbazole or derivatives thereof, polyarylene derivatives having an aromatic amine in the side chain or main chain, polymers containing aromatic amines such as arylamine derivatives and triphenyldiamine derivatives, etc. Is mentioned. In the inorganic _{materials, Cu 2 O, Cr 2 O} 3, Mn 2 O 3, NiO, CoO, Pr 2 O 3, Ag 2 O, MoO 2, ZnO, TiO 2, V 2 O 5, Nb 2 O 5, Examples include transition metal oxides such as Ta ₂ O ₅ , MoO ₃ , WO ₃ , MnO ₂ , and inorganic compounds containing one or more nitrides and sulfides of the transition metals, but the present invention is not limited to these. Absent.

  These organic materials are dissolved or stably dispersed in a solvent to form an organic interlayer ink. Examples of the solvent for dissolving or dispersing the organic interlayer material include toluene, xylene, acetone, anisole, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone alone or a mixed solvent thereof. Of these, aromatic organic solvents such as toluene, xylene, and anisole are preferable from the viewpoint of solubility of the organic interlayer material. Moreover, surfactant, antioxidant, a viscosity modifier, a ultraviolet absorber, etc. may be added to organic interlayer ink as needed.

  As these interlayer materials, it is preferable to select a material having a work function equal to or higher than that of the hole transport layer 104, and more preferable to have a work function equal to or lower than that of the organic light emitting layer 105. This is because an unnecessary injection barrier is not formed when carriers are injected from the hole transport layer 104 into the organic light emitting layer 105. Further, in order to obtain the effect of confining charges that could not contribute to light emission from the organic light emitting layer 105, the band gap is preferably 3.0 eV or more, more preferably 3.5 eV or more.

  As a method for forming the interlayer 105, depending on the material, dry film forming methods such as resistance heating vapor deposition, electron beam vapor deposition, reactive vapor deposition, ion plating, and sputtering, ink jet printing, letterpress printing, etc. Existing film forming methods such as a wet film forming method such as a method, a gravure printing method, and a screen printing method can be used, but the present invention is not limited thereto.

  In the case of a top emission type element, the organic light emitting layer 106 according to the embodiment of the present invention can be laminated after the interlayer 105 is formed. When the display light emitted from the organic light emitting layer 106 is monochromatic, it is formed so as to cover the interlayer 105. However, in order to obtain multicolor display light, it is preferably used by performing patterning as necessary. it can.

  Examples of the organic light-emitting material forming the organic light-emitting layer 106 include coumarin-based, perylene-based, pyran-based, anthrone-based, porphyrin-based, quinacridone-based, N, N′-dialkyl-substituted quinacridone-based, naphthalimide-based, N, N′-. Diaryl-substituted pyrrolopyrrole, iridium complex, and other luminescent dyes dispersed in polymers such as polystyrene, polymethylmethacrylate, and polyvinylcarbazole, and polyarylene, polyarylene vinylene, and polyfluorene polymers Examples of the material include, but are not limited to, the present invention.

  These organic light emitting materials are dissolved or stably dispersed in a solvent to form an organic light emitting ink. Examples of the solvent for dissolving or dispersing the organic light emitting material include toluene, xylene, acetone, anisole, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or a mixed solvent thereof. Among them, aromatic organic solvents such as toluene, xylene, and anisole are preferable from the viewpoint of the solubility of the organic light emitting material. Moreover, surfactant, antioxidant, a viscosity modifier, a ultraviolet absorber, etc. may be added to organic luminescent ink as needed.

  In addition to the polymer materials described above, 9,10-diarylanthracene derivatives, pyrene, coronene, perylene, rubrene, 1,1,4,4-tetraphenylbutadiene, tris (8-quinolato) aluminum complex, tris (4-methyl) -8-quinolate) aluminum complex, bis (8-quinolate) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolate) aluminum complex, tris (4-methyl-5-cyano-8-quinolate) Aluminum complex, bis (2-methyl-5-trifluoromethyl-8-quinolinolato) [4- (4-cyanophenyl) phenolate] aluminum complex, bis (2-methyl-5-cyano-8-quinolinolato) [4- ( 4-cyanophenyl) phenolate] aluminum complex, tris (8-quino) Norato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, poly-2,5-diheptyloxy-para-phenylene vinylene A low molecular weight light emitting material such as can be used.

  As a method for forming the organic light emitting layer 106, depending on the material, dry film forming methods such as resistance heating vapor deposition method, electron beam vapor deposition method, reactive vapor deposition method, ion plating method, sputtering method, ink jet printing method, letterpress Existing film forming methods such as a wet film forming method such as a printing method, a gravure printing method, and a screen printing method can be used, but the present invention is not limited thereto.

  Next, the second electrode 107 according to the embodiment of the present invention is formed on the organic light emitting layer. A specific material for the second electrode 107 is a single metal such as Mg, Al, or Yb, or a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the interface in contact with the light emitting medium layer 112. Al or Cu having high conductivity may be laminated and used. Alternatively, in order to achieve both electron injection efficiency and stability, one or more metals such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, and Yb having a low work function and stable Ag, An alloy system with a metal element such as Al or Cu may be used. Specifically, alloys such as MgAg, AlLi, and CuLi can be used. In addition, a transparent conductive film such as a metal composite oxide such as ITO (indium tin composite oxide), indium zinc composite oxide, or zinc aluminum composite oxide can be used.

  Since these counter electrodes 107 in the top emission structure transmit the display light emitted from the light emitting medium layer 112, they need to be transparent to the visible light region. In the case of simple metals such as Mg, Al, and Yb, the thickness is preferably 10 nm or less, and more preferably within 2-7 nm. The transparent conductive film can be suitably used by adjusting the film thickness so as to maintain an average transmittance of visible light wavelength of 85% or more.

  Depending on the material, the second electrode 107 may be formed by a dry film formation method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method, an ink jet printing method, or a gravure. Existing film forming methods such as a wet film forming method such as a printing method and a screen printing method can be used, but the present invention is not limited to these.

  For example, the sealing body 108 is sealed by adhering the sealing body 108 and the substrate to the periphery of the substrate 101 on which the first electrode 102, the partition wall 103, the light emitting medium layer 112, and the second electrode 107 are formed. A stop is made. At this time, in the top emission structure, display light radiated from the light emitting medium layer through the sealing body 108 on the side opposite to the substrate 101 side is extracted, so that light transmittance is required for the visible light region. It is preferable that the average transmittance of visible light wavelength is 85% or more as light transmittance.

  For example, the sealing body 208 is formed by using a glass cap or a metal cap having a recess with respect to the substrate 101 on which the first electrode 102, the partition wall 103, the light emitting medium layer 109, and the second electrode 107 are formed. Sealing is performed by adhering the cap and the substrate with an adhesive around the periphery of the organic light emitting medium layer and the second electrode so that a recess is formed in the air. By forming a hygroscopic agent in the recess and sealing under an inert gas such as nitrogen gas, element degradation due to moisture, gas, or the like can be prevented.

  Further, as shown in FIG. 5, the sealing body 108 has a resin layer on the sealing material 109 with respect to the substrate 101 on which the first electrode 102, the partition wall 103, the light emitting medium layer 112, and the second electrode 107 are formed. 110 may be provided, and the sealing material and the substrate may be bonded to each other with the resin layer 110.

At this time, the material of the sealing material 109 needs to be a base material having low moisture and oxygen permeability. Examples of the material include ceramics such as alumina, silicon nitride, and boron nitride, glass such as alkali-free glass and alkali glass, quartz, and moisture resistant film. Examples of moisture-resistant films include films formed by CVD of SiOx on both sides of plastic substrates, films with low permeability and water-absorbing films, or polymer films coated with a water-absorbing agent. The water vapor transmission rate is preferably 10 ⁻⁶ g / m ² / day or less.

  Examples of the resin layer 110 include a photo-curing adhesive resin made of an epoxy resin, an acrylic resin, a silicone resin, a thermosetting adhesive resin, a two-component curable adhesive resin, an ethylene ethyl acrylate (EEA) polymer, and the like. Acrylic resins, vinyl resins such as ethylene vinyl acetate (EVA), thermoplastic resins such as polyamide and synthetic rubber, and thermoplastic adhesive resins such as acid-modified products of polyethylene and polypropylene. As an example of a method for forming the resin layer 110 on the sealing material, a solvent solution method, an extrusion lamination method, a melting / hot melt method, a calendar method, a nozzle coating method, a screen printing method, a vacuum laminating method, a hot roll laminating method And so on. A material having a hygroscopic property or an oxygen absorbing property may be contained as necessary. The thickness of the resin layer 110 formed on the sealing material 109 is arbitrarily determined depending on the size and shape of the organic EL element to be sealed, but is preferably about 5 to 500 μm.

  The substrate 101 on which the first electrode 102, the partition wall 103, the light emitting medium layer 112, and the second electrode 107 are formed and the sealing body 108 are bonded together in a sealing chamber. When the sealing body 108 has a two-layer structure of a sealing material and a resin layer 110 and a thermoplastic resin is used for the resin layer 110, it is preferable to perform only pressure bonding with a heated roll. When a thermosetting adhesive resin is used, it is preferable to perform heat curing at a curing temperature after pressure bonding with a heated roll. In the case where a photocurable adhesive resin is used, curing can be performed by further irradiating light after pressure bonding with a roll. Note that although the resin layer 110 is formed over the sealing material 109 here, the resin layer 110 may be formed over the substrate and attached to the sealing material 109.

  Before or instead of sealing with the sealing material 109, for example, as the passivation film, the sealing body 108 formed with an inorganic thin film can be used, or these can be combined. Examples of the passivation film include, but are not limited to, silicon nitride, aluminum oxide, silicon oxide, calcium fluoride, and the like. A material that is an insulator and is stable against water and oxygen can be used in vacuum film formation, such as resistance heating evaporation, electron beam evaporation, reactive evaporation, ion plating, and sputtering. Can be used to form a film.

  As the first electrode (pixel electrode) 102 provided on the substrate 101, an active matrix substrate 101 provided with an ITO thin film on chrome was used. The size of the substrate 101 is 5 inches diagonal, and the number of pixels is 320 × 240.

  A partition wall 103 was formed in such a shape as to cover an end portion of the first electrode 102 provided on the substrate 101 and partition a pixel. The partition wall 103 is formed by using a positive resist, a product name “ZWD6216-6” manufactured by ZEON Corporation, with a thickness of 2 μm on the entire surface of the substrate 101 by a spin coater method, and then using a photolithography method to a width of 40 μm. A partition wall 103 was formed by patterning. As a result, a pixel area of 960 × 240 dots and a pitch of 0.12 mm × 0.36 mm was defined.

  On the first electrode 102, as a hole transport layer 104, molybdenum oxide and indium oxide having a thickness of 50 nm were co-deposited by a vacuum deposition method, and a pattern was formed by a shadow mask method. The ratio of co-evaporation was adjusted using a film formation rate monitor installed in each evaporation source. The mixing ratio of molybdenum oxide and indium oxide is 1: 4. The hole transport layer thus formed had a total average reflectance of 65% in the visible light region. The pattern region was formed using a metal mask having an opening of 120 mm × 100 mm so as to be formed on the entire display region.

  Thereafter, a pixel electrode 102, a partition wall 103, and a hole transport layer 104 formed on the substrate 101 are formed using an ink in which a polyvinyl carbazole derivative, which is a material of the interlayer 105, is dissolved in toluene so as to have a concentration of 0.5%. Is set as the printing substrate 302 of the relief printing apparatus 300 shown in FIG. 6, and the interlayer 105 is relief-printed according to the line pattern just above the hole transport layer 104 on the pixel electrode 102 sandwiched between the partition walls 103. Printing was performed by the printing method. At this time, an anilox roll 305 of 300 lines / inch and a relief printing plate 307 made of a photosensitive resin were used. The film thickness of the interlayer 105 after printing and drying was 10 nm.

  A pixel electrode 102, a partition wall 103, and a hole transport layer formed on the substrate 101 using an organic light emitting ink in which a polyphenylene vinylene derivative, which is an organic light emitting material of the light emitting medium layer 112, is dissolved in toluene so as to have a concentration of 1%. 104 and the interlayer 105 are set as the printing substrate 302 of the relief printing apparatus 300, and the light emitting medium layer 112 is printed by the relief printing method in accordance with the line pattern just above the interlayer 105 sandwiched between the partition walls 103. It was. At this time, an anilox roll 305 of 150 lines / inch and a relief plate 307 made of a photosensitive resin were used. The thickness of the light emitting medium layer 112 after printing and drying was 80 nm.

  Thereafter, as a counter electrode 107, a calcium film is formed with a thickness of 5 nm by a vacuum deposition method using a metal mask having an opening of 120 mm × 100 mm, and then an aluminum film is transmissive using a metal mask having an opening of 124 mm × 104 mm. In order to obtain a film, a film was formed with a thickness of 5 nm.

Thereafter, sealing was performed by forming a silicon nitride film with a thickness of 300 nm using the CVD method as the sealing body 108. When the organic electroluminescent display device 100 thus obtained was driven, a display characteristic of 150 cd / m ² at a luminance of 5 V, 12 cd / A at a luminous efficiency of 20 mA / cm ² was obtained, and a uniform light emission state without luminance unevenness Met.

Before the formation of the hole transport layer 104, the same procedure as in Example 1 was performed. As the hole transport layer 104, vanadium oxide (V ₂ O ₅ ) and zinc oxide (ZnO) having a thickness of 50 nm were vacuumed. A pattern was formed by a shadow mask method by co-evaporation using a vapor deposition method. At this time, the mixing ratio of vanadium oxide and zinc oxide is 1: 7. Thereafter, the interlayer 105, the light emitting medium layer 112, the counter electrode 107, and the sealing material 108 were produced in the same procedure as in Example 1.

When the organic electroluminescent display device 100 thus obtained was driven, the display characteristics of 100 cd / m ² at a luminance of 5 V and 10 cd / A at a luminous efficiency of 20 mA / cm ² were obtained, and uniform light emission was achieved without uneven brightness. It was in a state.

(Comparative Example 1)
Before the formation of the hole transport layer 104, it was prepared in the same procedure as in Example 1, and PEDOT / PSS (polyethylenedioxythiophene / polystyrene sulfonic acid) was used as the hole transport layer 104 to a thickness of 50 nm by spin coating. A film was formed. Thereafter, the interlayer 105, the light emitting medium layer 112, the counter electrode, and the sealing material were produced in the same procedure as in Example 1.

When the organic electroluminescent display device 100 thus obtained was driven, a display characteristic of 9 cd / A was obtained at a luminance of 6 cd, a luminance of 100 cd / m ² , a luminous efficiency of 20 mA / cm ² , and a uniform light emitting state. Met.

  By using a hole transport layer as an inorganic compound and also having a function as a reflective layer, it becomes possible to take out light that has been deactivated as guided light in the organic thin film, and by covering at least a part of the partition, The display light absorbed in the light was extracted, and a high-efficiency top emission organic electroluminescence display device was obtained.

  Then, as a result of performing an accelerated test on the manufactured Examples 1 and 2 and Comparative Example 1 in a constant temperature and high humidity environment at a temperature of 60 ° C. and a humidity of 95%, a dark spot was found on the light emitting surface of Comparative Example 1 after 1400 hours. However, in Examples 1 and 2, a dark spot did not occur even after 2000 hours, and the organic electroluminescence display device 100 with high display efficiency without light display defect could be obtained.

DESCRIPTION OF SYMBOLS 100 ... Organic electroluminescent display device 101 ... Substrate 102a ... First electrode (anode)
102b ... first electrode (cathode)
DESCRIPTION OF SYMBOLS 103 ... Partition 104 ... Hole transport layer 105 ... Interlayer 106 ... Organic light emitting layer 107a ... Second electrode (cathode)
107b ... second electrode (anode)
DESCRIPTION OF SYMBOLS 108 ... Sealing body 109 ... Sealing material 110 ... Resin layer 112 ... Luminescent medium layer 300 ... Letterpress printing apparatus 301 ... Stage 302 ... Printed substrate 303 ... Ink tank 304 ... Ink chamber 305 ... Anilox roll 306 ... Doctor 307 ... Letterpress 308 ... Plate cylinder 309 ... Ink layer

Claims (20)

  An organic electroluminescent device having at least a hole transport layer made of an inorganic compound and an organic light emitting layer between a first electrode and a second electrode on a substrate, wherein light emitted from the organic light emitting layer An organic electroluminescent element which is reflected by the hole transport layer.   The organic electroluminescent device according to claim 1, wherein the inorganic compound is an inorganic compound containing one or more transition metals.   The organic electroluminescent element according to claim 1, wherein the inorganic compound includes a metal oxide material having an oxygen defect and exhibiting a metallic luster.   The organic electroluminescence device according to claim 3, wherein the work function of the metal oxide material is 4.0 eV or more and 6.5 eV or less. The metal oxide material is any one of TiO ₂ , ZnO, NiO, Ta ₂ O ₅ , MoO ₂ ), silver oxide (Ag ₂ O, CoO, Cr ₂ O ₃ , RuO ₂ , In ₂ O ₃ ). The organic electroluminescent element according to claim 3 or 4. The inorganic compound includes a hole transport material and a metal oxide material having an oxygen defect and exhibiting a metallic luster, and the hole transport material includes Cu ₂ O, Cr ₂ O ₃ , Mn ₂ O ₃ , NiO, It includes any one of CoO, Pr ₂ O ₃ , Ag ₂ O, MoO ₂ , ZnO, TiO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O ₅ , MoO ₃ , WO ₃ , and MnO _2. The organic electroluminescent element according to any one of claims 3 to 5.   The organic electroluminescent device according to claim 1, wherein an average reflectance of the hole transport layer with respect to light emitted from the organic light emitting layer is 50% or more.   8. The organic electroluminescent element according to claim 1, wherein the hole transport layer has a thickness of 10 nm to 100 nm.   9. The organic electroluminescent element according to claim 1, further comprising a partition wall that partitions at least the organic light emitting layer into a plurality of pixels.   The organic electroluminescent device according to claim 9, wherein the hole transport layer covers at least a part of the partition wall.   The second electrode is a transparent electrode, wherein the first electrode, the hole transport layer, and the organic light emitting layer are laminated in this order between the first electrode and the second electrode. Item 11. The organic electroluminescent device according to any one of Items 1 to 10.   The first electrode is a transparent electrode, wherein the first electrode, the organic light emitting layer, and the hole transport layer are laminated in this order between the first electrode and the second electrode. Item 12. The organic electroluminescent device according to any one of Items 1 to 11.   13. An image display device comprising the organic electroluminescent device according to claim 1 as a display device.   14. An illuminating device using the organic electroluminescent element according to claim 1 as a light emitting element. Between the first electrode and the second electrode on the substrate, a hole transport layer made of an inorganic compound, and an organic light emitting layer, a method for producing an organic electroluminescent device having at least,
Forming a first electrode on the substrate;
Forming a hole transport layer that reflects light emitted from the organic light emitting layer on the first electrode;
Forming an organic light emitting layer on the hole transport layer;
Forming a second electrode on the organic light emitting layer;
The manufacturing method of the organic electroluminescent element which has this.   The method of manufacturing an organic electroluminescent element according to claim 15, wherein the hole transport layer is formed by mixing a plurality of inorganic compounds by a dry film forming method.   The method according to claim 16, wherein the hole transport layer is formed by mixing a plurality of inorganic compounds by co-evaporation.   18. The method of manufacturing an organic electroluminescent device according to claim 17, wherein the inorganic compound includes a metal oxide, and oxygen defects are generated during vapor deposition or after film formation of at least one type of metal oxide.   19. The method of manufacturing an organic electroluminescent element according to claim 15, wherein the organic light emitting layer is formed by depositing an ink containing an organic light emitting material by a wet film forming method. Forming a partition partitioning a plurality of pixels on the substrate;
20. The method of manufacturing an organic electroluminescent element according to claim 15, wherein the hole transport layer is formed on the entire display region including the partition walls and the first electrode.

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